Secretory and endocytic processes in several cell types are currently under investigation. Cell dissociation and short term culture (up to 1 month) methods have been established for rat exorbital lacrimal, parotid and pancreatic acinar cells. These cultures are being used to study various aspects of the secretory process. Emphasis is placed on morphological, cytochemical and biochemical characterization of the cultured cells. Uptake and fate of both soluble phase and membrane bound markers by exocrine acinar cells are being examined in vivo and in vitro. The lysosomal system and its role in endocytic processes is also under study.